The long term goal of this thesis project will be to determine the role of specific types of gamma-aminobutyric acid type A (GABAA) receptors in the mammalian hypothalamus in mediating the expression of gender-specific sexual behaviors. It has been experimentally established that gonadal steroids act during a perinatal critical period to induce morphological differences in the mammalian brain which provide the basis for gender- specific sexual behaviors. Within the hypothalamus, it has been shown that specific nuclei, namely the Ventromedial nucleus (VMN) and the preoptic area (POA), play essential roles in the expression of these behaviors in adult rats. Specifically, it is believed that activity within the VMN facilitates female sexual behaviors whereas activity within the POA inhibits female sexual behaviors and is critical for the expression of male sexual behaviors. Moreover, GA BAA-mediated transmission in these areas has been implicated in the control of adult sexual behavior and data from our laboratory suggests that significant gender-dependent differences in GABAA receptor function are found between VMN neurons in female versus male neonatal rats. The specific goals of this project will be to determine if these gender-specific differences in GABAA receptor properties are regulated by exposure to steroids during development, and if these differences in function lead to different patterns of synaptic transmission in the female versus male hypothalamus which then contribute to the expression of appropriate behaviors.